Twitter's outage down to a 'double-whammy' systems failure

Twitter's outage was the result of its data centre and backup
systems failing simultaneously rather than a surge in
Olympic-themed tweets, the social networking site has
explained..

For nearly two hours on 25 July Twitter users worldwide had to
stop their onslaught of tweets about their Olympics excitement (or
dread) -- an onslaught which, according to Twitter's vice president
of engineering Mazen Rawashdeh, had nothing whatsoever to do with
the technical breakdown.

"We are sorry. Many of you came to Twitter earlier today
expecting, well, Twitter," said Rawashdeh in a blog statement. "I
wish I could say that [the] outage could be explained by the
Olympics or even a cascading bug. Instead, it was due to this
infrastructural double-whammy."

"Data centres are designed to be redundant: when one system
fails (as everything does at one time or another), a parallel
system takes over. What was noteworthy about today's outage was the
coincidental failure of two parallel systems at nearly the same time."

Some users could still access the site via smartphones and
Facebook, but otherwise the blackout prevented us from reading the 140-character musings
from the Olympic athletes registered and expected to tweet during
the Games -- no bad thing, according to Sebastian Coe, who recently said he found there to be "quite a close correlation
between the number of tweets at competitive times and the level of
under-performance".

It's the second blackout in five weeks for the micro-blogging
site -- on 21 June the site fell foul of a "cascading bug" that
affected a series of software components. It was, again, down for
around two hours and, again, Rawashdeh had to bat away
suggestions that the failure was down to a sporting event -- in
June, it was Euro 2012, which triggered users to send 15,000 tweets
a second during its busiest times.

The site's glitches are few and far between compared to its
early days and, Rawashdeh says, Twitter is continuing to bolster
the system: "We are investing aggressively in our systems to avoid
this situation in the future."